I hear scientist are researching technology to upload minds up to computer just like uploading music to your PC from you iPod. If they succeed, could it happen ? Say if you just upload two people's minds up to a computer, than download them back to the other person's brain.

"I hear scientist are researching technology to upload minds up to computer"

 

http://xkcd.com/285/

I doubt scientists are doing that, although it depends on what has to be understood under "mind".

 

Anyway, some traits can be transfered between two individuals, usually we use speech and writing to do so.(ideas, beliefs and things like that)

Other traits are harder, since they're more hardware then software.(potential size of memory for example)

In the distant future, I can almost accept it'd be possible to scan the current physical content of a persons brain (synapses, connections between them ...), and "upload" into a computer.

 

"Download" would be a whole other ballgame, as that'd require re-wiring the content of the destination brain, and there wouldn't be a 1-to-1 match of bits to re-wire; even if a mechanism were found (magic nanotechnology).

How would you extract the data that you want to upload into the iPod? Where is the USB port (or equivalent interface) with the human brain?

The human brain transmits information in a very different way than a computer does. Even if some way were discovered of converting the brain's electrochemical signals to bits, it would probably not work to 'run' the person's mind like software on a computer, and definitely not to 'download' someone's mind into another person's brain. That would require actually physically rewiring the neurons of whoever received the 'mind transplant'. It would be something like tring to put Java code through a C++ compiler.